Headway 38120L/S

[hagerty1]

Sorry if I am in the wrong area.
Very simple I think.
I have a friend that has an Elf. It has a Nominal 48V 10AH pack built with Headway E 38120 Cells
The pack is a 16S 1 P with a bms.

Issue 1 he let the pack drain to a total pack voltage of 8.7V
Fast charger (15 amp) would not even crank up it just showed full charge immediately.
Slow charger took a while but finally started to bring voltage up. It got to around 33 volts.
I connected fast charger and it then started charging. Issue became that when we came out an hour later the vom meter showed
69 volts. I unplugged it. Nothing seemed hot. But I could not understand why the bms did not stop off the charge process.
Even stranger is when we put a load on the pack the Volt meter (a plain jame sears units) showed a voltage spike to 71 volts under load.
The battery pack is factory
The BMS is integrated to the pack
The chargers are factory. All from Organic Transit.
I am not sure if I can tell my friend it is even safe to use the battery pack ?????????
I have only dealt with Lithium Ion. I am not familiar with Lifepo cells. I know if I took my Lithium Ions down to 1/2 volt each in a pack
I would send it to cell heaven.
I do not know how deeply you can discharge Lifepo and still recharge them. I am very concerned about the voltage spike under load with no charger
or other input source.....that's a new one on me. I also seems the BMS has failed to protect from deep dischrge and or over charge.
Should this pack just be discarded and start over ????
I don't want my buddy getting hurt. Any ore than what he paid for an Elf...
Any help appreciated.
Jim

 

[teklektik]

The pack is a 16S 1 P with a bms.
...when we put a load on the pack the Volt meter (a plain jame sears units) showed a voltage spike to 71 volts under load.

71V/16 = 4.4V/cell

Either your charger is very sick or your DMM needs a new battery...
I'm thinking the second....

 

[amberwolf]

The whole thing sounds messed up.

I'd check the voltmeter battery first, cuz a bad battery will show too-high voltages.

If that's not the problem, then:

The charger shouldn't be able to get it beyond about 58 volts, maybe 58.4 max, even in order to do balancing. If it can go as high as 69V, that is the wrong charger for the pack or the charger is broken.


Regardless of the voltmeter battery: The BMS shouldn't have allowed discharge past whatever it's cell-level LVC is, at worst maybe 2.something volts. BMSs drain the pack they are attached to, some only drain certain cells, some the whole pack, in order to power themselves. Over a very long time of sitting there without recharging, they coudl kill a pack if they don't have any internal cutoff mechanism that disconnects the BMS from the pack once the pack is below LVC.

But a good BMS won't kill a pack like that, or allow it to go anywhere near what that pack got to, even if it's actively being discharged, much less just let sit.

It also shouldn't ever let the charger keep charging the pack past HVC, even if the charger is wrong or defective and is set higher than the pack's full charge voltage should ever be at.

So either wya, the BMS is bad.


As for the cells...you might still be able to use the cells for a non-high-drain application, but they probably won't ever again have the capability or capacity they should.

What were the individual cell voltages? (you can't count on them all being the same, especially when drained down that low. If some went negative, definitely don't use them. If you don't know, don't use any of them because you can't know now which might have.)

 

[dmwahl]

Most basic BMSes will continuously drain about 0.5mA, so if he discharged it and let it sit for too long it's not surprising that the BMS could have done it. Not entirely the fault of the BMS.

As far as troubleshooting the cells, here's what I'd suggest.
1. Get a second multimeter and make sure it agrees with the first within a few percent, alternatively, measure some known voltage sources like a fresh 9V battery (should read 9-9.5V brand new) and some new alkaline batteries (~1.5V new). You need to know whether or not it can be trusted before doing anything with it.
2. Measure charger output voltage when it's not connected to the pack. As AW said, should be around 58V.
3. Measure each individual cell voltage at rest and record the values. If they're anywhere from 2.0V-3.4V after the pack has rested for a day or two, they may be ok. If they're below about 3.0V, charge slowly until they're around 3.5-3.6V each. I'd do it with a bench supply to control current and voltage, but a single cell LiFePO4 charger that puts out around 1A should be fine.

If you can bring the cells back to normal voltage, they don't get too warm when charging/discharging, and they are stable after resting for a few days, the pack may be OK. It's doubtful that they're totally undamaged if it was really down to 8.7V, but may still have a useful life left.

 

[hagerty1]

More on Organic Transit and the Elf Headway battery pack. After my buddy giving up on the pack....He lives in Fla. Me in Ohio.
He found out pedaling this thing is...FORGET IT>>>>>any hills....I'm talking Fla hills that we in Ohio call bumps in the road he can't do it.
Long story on how he got this $7,000 POS..... He finally sent me the pack a few days ago. I build packs for friends only and offered to make him
a lithium Ion pack with 18650 cells but he could not seem to get his head around measuring the battery compartment so I said just send me the
old pack a 16s 1p with headway 3812s 10ah cells...............What a shocker.........
1) The solar Panel on his model goes directly to the pack. I discovered the solar panel has a short that is known to Organic but they felt no need to inform the customers I know because they told me so over the phone but offered to tell me how to fix it...... This is what may have totally killed the pack voltage. My buddies VOM was also a P.O.S. so I can not say anything about any voltage measurements I did while visiting him as described in previous posts. When I received the pack it showed total voltage of 12.3 volts at the output cell connection points.
2) I was SHOCKED to see that even though the BMS has monitor leads to each cell the charger also is connected DIRECT to the pack bypassing the BMS completely FTF.......no regulation of charge voltage whatsoever.......and as the solar panel also bypasses the BMS it allows the pack to totally discharge.....NICE...

I have since disconnected the BMS and have charged the pack several times. It seems to take a 3.5-3.6 volt per cell charge voltage but flattens at at pack
voltage of around 53.3-53.5 volts or around 3.3 volts per cell. I have charged in goups of 2 s using Turnigy Imax and G.T. chargers. All cut off showing FULL
when set to LiFe chemisty and 2s config. Chargers show end voltage of 2s at 7.2 volts. Upon disconnection of charger my VOM (several) shows 6.95 volts or
3.475 volts each.
Is this normal for these cells to be full at under the rated full charge of 3.65 volts?
I hooked the pack up to my trike that runs a 14S x 14P pack and ran around for quite a while and the Headway pack seemed fine as long as I did not run it through the BMS.
I thought maybe 1 bad cell but I do not see this in doing in pair charging.
BIG QUESTION>>>> Is the pack fine at full charge of around 53 volts +.3-.5 ???
When I charge the full pack without bms using my 14s Li Ion charger ate 58.8 volts it cuts off with pack just over 58 volts and then the pack settles withing an hour to the 53.3 volts...... I intend to make him a new pack in any event this is just for my personal knowledge.

Any help please advise...
And P.S.
Avoid Organic......what I saw in their construction looked like it came for some third world hut......Great frame but every thing else is CRAP